Exposure can be both a simple and complex subject. I’ll cover two topics in this post - a more detailed discussion about Correct exposure and the Give and Take of Photography.
In all the automatic modes, the camera’s firmware turns on the light meter, reads the light hitting the sensor, activates an algorithm, which sets the Shutter Speed, Aperture and ISO values and captures the image as you press the Shutter Release button. All this happens within milliseconds. What you see is an exposed image on your LCD screen that looks pretty good. Maybe.
In Manual Mode, you set the ISO value, adjust the Shutter Speed and Aperture, press the Shutter Release and view the image on the camera’s LCD screen.
If you’re happy with the result, then the exposure’s “correct”.
If you’re not happy with the image, you re-adjust either the Shutter Speed or Aperture value and capture another image. You repeat this procedure until you’re happy with the resulting image. it could take you 3 or 4 attempts. This is a trial and error approach.
As you can see, “correct” exposure is a creative, personal choice. “Correct” all depends on your personal choice. There is no set Shutter Speed or Aperture combination that gives you a “correct” image exposure for every image.
Shutter Speed and Aperture control exposure. But what about ISO you ask?
Briefly, ISO does not affect exposure. It also does not make the sensor more sensitive to light!! In a later post, I’ll discuss ISO in more detail.
In digital photography, exposure is the amount of light (Aperture) and the amount of time (Shutter Speed) it’s allowed to enter through the lens and reach the camera’s sensor.
The key take away here is there is no such thing as a “correct” exposure.
The Give and Take of Photography
What do I mean by Give-and-Take??
As discussed above, photographic exposure involves two camera settings: Shutter Speed and Aperture.
Shutter Speed’s give-and-take impacts the subject matter’s blurring. If your selected Shutter Speed is too slow, the resulting subject may be blurred where you wanted it crisp and sharp. On the other hand, if you want to blur the subject’s motion and the applicable Shutter Speed is too fast, the resultant image is crisp and sharp.
If you have to use a slow Shutter Speed due to a low light level and you’re shooting hand held, you may get a blurred image due to camera shake. (You forgot your tripod at home or you haven’t purchased one yet.)
If you’re using a very long telephoto lens, e.g., around 70mm or more, and shooting handheld, again you might end up with a blurred image due to camera shake if the Shutter Speed is too slow.
As you can see, there is no perfect Shutter Speed for every image. To obtain a sharp or blurred image all depends on a number of factors.
Aperture’s give-and-take impacts an image’s Depth-of-Field (DoF). A wide open Aperture renders a shallow DoF, while a small Aperture produces an image with great DoF.
The image on the left was shot at f 2.8, while the image on the right was shot at f 22.
A wide open Aperture, e.g., f 1.4, lets a lot of light in. A very small Aperture, e.g., f 22, reduces the amount of light a great deal. However, a small Aperture setting also introduces diffraction. Diffraction means the edges of your photograph grows progressively less sharp at smaller and smaller aperture values – f/16, f/22, and so on.
The following image shows two Aperture examples - the one on the left represents a wide Aperture setting, where as the one on the right represents a small Aperture setting. Notice the increased curve to the light as it enters the smaller Aperture setting. This is because light bends as it passes an edge. This can cause the edges of an image to be less sharp than the centre.
That completes this brief overview of exposure and the Give and Take of Photography.
If you have any specific questions, please email me at email@example.com. I’ll be happy to answer any questions and may include your question and answer in a future post.
In this post, I’ll review the camera’s digital sensor and memory cards. I’ll give a brief over of the sensor, with a link to a more detailed well written description of the sensor and how it works.
For the Memory cards, I’ve compiled the most current information from various sources.
Your Camera’s Sensor - Overview
Do you have any idea how the darn thing actually works? Coming from an analog film background, I initially thought it might be something akin to film in some esoteric fashion.
Nope, not even close!! Boy was I wrong.
Did you know a digital sensor doesn’t record/see colour? That’s correct.
A digital sensor’s “photosites”, or light cavities (pixels), only record photons of light that enter them. The photons enter the photoshite and strike a photodiode. When a photon strikes the photodiode an analog electrical signal is produced. The greater the number of photons, the greater the analog electrical signal. The analog electrical signal is converted to a digital signal that ranges in value from 0 - 255, where 0 = pure black and 255 = pure white. In other words, the sensor’s digital signal only sees the light as series of black to white, or a grayscale of tones.
How many photsites are on a sensor? That depends on the sensor size, e.g., a Panasonic Lumix ZS80’s sensor is 1” x 2.3” and has 20,300,000 pixels. A Sony A7Riii’s sensor is 24” x 35.9” and has 42.56 million pixels.
So where does the colour in the image come from?
Colour comes from a Bayer colour filter array that sits on top of each photosite, or pixel on the sensor.
You’ll notice there are more green coloured filters in the array. The green pixels produces an image which appears less noisy and renders finer image details.
There are two types of digital sensors - CCD and CMOS. Because of the manufacturing differences, the following details the differences between CCD and CMOS sensors.
- CCD sensors create high-quality, low-noise images. CMOS sensors, traditionally, are more susceptible to noise
- Each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip tends to be lower. Many of the photons hitting the chip hit the transistors instead of the photodiode
- CMOS consumes little power. Implementing a sensor in CMOS yields a low-power sensor
- CCDs consumes lots of power, as much as 100 times more power than an equivalent CMOS sensor
- CMOS chips are simpler to manufacture, so they are inexpensive compared to CCD sensors
- CCD sensors are more mature and are of higher quality and have more pixels.
Based on the above, you can see CCDs are used in cameras focusing on high-quality images with lots of pixels and excellent light sensitivity, e.g., medium format cameras.
CMOS sensors tended to have lower quality, lower resolution and lower sensitivity. However, CMOS sensors have improved to where they’re almost equal with CCD sensors today. CMOS cameras are less expensive and have great battery life.
For a more detailed, yet clear sensor description, click here.
OK, Memory Cards don’t really have a lot to do with using your camera in Manual mode. But I thought the information might be of interest.
Most of today’s devices use either SD or microSD cards, which you can determine by looking at the card slot on your camera. DSLR cameras use Compact Flash memory cards.
The image set below shows a SDHC card 32GB, a SDXC card 63GB and a Compact Flash card 32BB.
Storage capacity is simple, it’s represented in gigabytes (GB). I t’s easy to assume that the bigger the number, the better, but in reality, this is not necessarily the case.
Not only can it be cheaper to use multiple smaller cards, you won’t live and die with just one card because they do degrade, get lost or experience data corruption.
Memory cards are not meant as a permanent storage device. After your shoot, transfer the image files to your computer, or an external hard drive. Then format the memory card in camera; never format the memory card in your computer. And always consider using a second external hard drive as a back-up drive for your image files.
How much storage do you need? Simple answer; it depends. A 4GB card holds about 280 RAW image files, or about 1,500 high quality JPEG files. A 128GB card would hold about 9,000 RAW image files. Whoa!!!! That’s a lot! If you shoot video, you’ll definitely need a 128GB U3 card!!
SD vs. SDHC vs. SDXC
The file system being used to store data determines a memory card’s capacity.
SD (secure digital) cards are the oldest, least used and limited to 2GB of storage.
SDHC (high capacity) cards can store up to 32 GB of data. SDXC (extended capacity) cards can store up to 2 terabytes (2000 GB) of data. These high capacity cards also come with a much higher price tag.
Older cameras may not be able to use the SDXC format, so make sure your device does support these larger cards before buying one.
Things can get a bit confusing, as the the card’s speed can be referred to by various designations. It’s represented in MB/s (megabytes per second), or a large number followed by an “X” or sometimes both.
The X designation is a marketing term — 1X represents 150 kb/s (kilobytes per second), so 600X is the same as a 90 MB/s rating (600 x 150 = 90,000). This number typically represent the “read” speed, which is generally higher than the “write” speed.
Write speed is how fast the card accepts image files from the camera. Read speed is how fast the card lets a computer read the image files during download.
This specification is represented on the card as a number inside of the letter “C” to represent the minimum write speed and is most important to those shooting video or very large images in burst mode.
There are four classes — 2, 4, 6 and 10 — which represent the minimum sustained megabytes per second (MB/s) write speed. The higher the number, the faster the sustained speed.
The point of this is to avoid your camera buffering and slowing down the image writing process.
UHS Speed Class
Faster SDXC memory cards will have the UHS, or Ultra High Speed, rating represented by a number inside the letter “U.” U1 means it’s 10 MB/s while U3 means it’s rated at 30 MB/s. Use this type of card to capture 4K video.
UHS Bus Class
Different from the UHS Speed Class, this rating refers to the “bus interface” and is represented by a Roman numeral. Think of the bus interface as the number of lanes on a freeway vs the UHS Speed Class, which represents the speed of individual cars.
Video Speed Class
If you’re trying to shoot extremely high-resolution video (4K or 8K), this class of cards — designated by the letter V and a number that ranges from 6 to 90 — offers the fastest sustained write speed.
SD and MicroSD Cards
Two of the most popular memory cards are SD and MicroSD cards. That’s because they’re readily available, affordable, and compatible with multiple cameras across many manufacturers. Their storage capacity and speed have increased dramatically in the last few years, but so has the price for premium cards.
It was only a few years ago that a 128GB SD card seemed like the pinnacle of the technology, but the new 1TB SD and MicroSD cards surpassed that milestone. These memory cards are not meant for the typical amateur photographer. Rather, they’re tailored for “prosumers” and professionals — just check the price tag. Even with big discounts, the majority of 1TB SD or Micro SD memory cards cost upwards of $300.
While the price may be steep for most, there are some significant advantages, especially if you record lots of high-quality footage. With 1TB of space, you don’t have to replace your card as often. Its read/write speeds can also handle most tasks from 4K video to 8K video, in some cases. Cards with a V60 or V90 rating are best suited for 8K, while V30-rated cards can handle 4K. For reference, a V30 rating means that there’s a constant write speed of 30MB/second, which keeps video files smooth and stutter-free.
If you have any specific questions, please email me at firstname.lastname@example.org. I’ll reply as soon as possible and may include your question and answer in a future post.
This series of Blog posts details how to use your digital camera in Manual Mode. I’ll try to keep each post fairly short, but don’t hold me to that statement. No one wants to read a long Blog post that just rambles on and on. Each post will detail one or two topics at a time (hopefully). I hope you find them easy to read and understand.
I’ve owned a few digital cameras over time - Canon DSLR (full-frame), Fujifilm X-T1 (cropped sensor) and currently, a Sony A7riii (full-frame). As for lenses, I won’t even bother going there. I’ve been practising and learning about digital photography for many years. Key word is practise - one rarely perfects photography.
If you have any specific topics or questions you’d like me to discuss, please email me your suggestions.
The illustration below shows a camera’s Mode Dial set to M (manual).
You’ve probably been using AUTO, or any of the other auto modes, e.g., portrait, landscape, close up, etc. for a while now. In these modes, the camera and its firmware determines the best exposure for the image. The simplicity of capturing a photo is the main attraction of these modes. However, as you gain more experience, you may find yourself wanting to control the camera yourself. That’s what these posts will be all about.
In this initial post, I’ll discuss two topics: the camera’s Diopter and give a brief overview of “correct” exposure.
The Camera’s Diopter
I wear glasses all the time. Looking through the Viewfinder can be an issue.
If you don’t wear glasses then the Viewfinder’s Diopter default setting may be perfectly sharp and focused. Congrats!!
The Diopter lets you adjust the Viewfinder’s image so everything is crips and focused. Todays DSLR and Mirrorless cameras all have a Diopter.
The following illustrates the Diopter for a DSLR camera.
The following illustrates the Diopter for a Mirrorless camera.
To adjust the Diopter, look through the Viewfinder with your glasses on, or without if you don’t wear any. Is the image crisp and in focus?
If yes, then you’re done!!
If not, slowly rotate the dial clockwise and/or countercheck wise until the image is crisp and sharp. That’s it, your done!!
Finally, I want to briefly discuss the concept of “correct exposure”. Photographers in general obsess over getting the correct exposure. Note how many times you see a photo online quoting the ISO, Aperture and Shutter Speed settings.
When using your camera’s auto modes, the camera’s firmware/algorithms do a pretty good job of setting an acceptable image exposure. I’m sure you were fairly happy with how your pictures turned out by using the auto modes. And for you, the exposures were correct.
I want to challenge the perception there is a “correct” exposure for a photo. I suggest there’s an “appropriate” exposure.
I’ll use two sample image to demonstrate my point.
The above image was my original exposure made on my iPhone. I let the camera’s firmware set the exposure while I concentrated on the image’s composition. Before I captured the image, I already had decided creatively what I wanted the final image to look like.
I feel the above version of the image is much more impactful and visually powerful. I converted it to B&W, but I also reduced the overall exposure. Plus, I darkened the shadows until there was very little detail in them. I feel this final image’s exposure is more “appropriate” to what my creative vision was.
Now let’s look at a colour image.
The exposure for the above image was what I originally set. I was primarily concerned about not over exposing the highlights in the snow. As you can see, this original exposure is quite flat with extremely low contrast. I imported the file into Lightroom Classic for post processing. Originally. I thought I might create a B&W image, but later decided to stay with colour.
Creatively, I modified the image to emphasis the light coming in from the upper left corner that creates the mid-tone texture in the snow. I also wanted to maintain the brightness along the edges of the drift’s shapes to bring out the overall contours of the snow’s form. The snow’s colour was always present in the original exposure. By making a few simple tweaks, I was able to enhance what’s already there. For me, this image is about the sense of the snow’s coolness and the texture. It’s about shape, form, light and detailed textures. I feel this exposure is more ”appropriate”.
I hope you found this first post informative and interesting. Stay tuned for further posts.
If you have any specific questions, please email me at email@example.com. I’ll reply as soon as possible and may include your question and answer in a future post.